In orthopaedic reconstruction, surgeons often replace damaged tissue resulting from trauma, pathological degeneration, or congenital deformity with autogenous grafts (Langer, R. and Vacanti, J. P. Science. 1993 260:920). Reconstructive surgery is based upon the principle of replacing these types of defective tissues with viable, functioning alternatives. The grafting of bone in skeletal reconstruction has become a common task of the orthopaedic surgeon with over 863,200 grafting procedures performed each year in the U.S. For cartilage replacement, there are over 1,000,000 procedures of various types performed each year and for ligament repairs, there are approximately 90,000 procedures performed per year (Langer, R. and Vacanti, J. P. Science. 1993 260:920). Currently, autografts (Friedman et al. Clin. Ortho. 1985 196:9; Jackson et al. Amer. J. Sports Med. 1990 18:1) (tissue taken from the patient) and allografts (Gadzag et al. J. Amer. Acad Ortho. Surg. 1995 3:1; Shinoet al. J. Bone and Joint Surg. 1988 7011:556; Jackson et al. Arthroscopy 1994 10:442)(tissue taken from a cadaver) are the most common replacement sources for the treatment of musculoskeletal problems. In repair of ligament injuries, such as injury of the anterior cruciate ligament (ACL), a segment of the patellar tendon has been frequently used (Jackson et al. Amer. J. Sports Med. 1990 18:1). For cartilage and bone repair, transplantation of autogenous grafts has been the current treatment of choice.
However, there are various problems associated with these treatments. For example, for autogenous tissue, key limitations are donor site morbidity where the remaining tissue at the harvest site is damaged by removal of the graft, and the limited amount of tissue available for harvesting. The use of allografts attempts to alleviate these problems. However, this type of graft is often rejected by the host body due to an immune response to the tissue. Allografts are also capable of transmitting disease. Although a thorough screening process eliminates most of the disease carrying tissue, this method is not 100% effective.
As a result of the limitations with conventional reconstructive graft materials, surgeons have looked to synthetic alternatives.
Synthetic ligament grafts or graft supports include carbon fibers, Leeds-Keio ligament (polyethylene terephthalate), the Gore Tex prosthesis (polytetrafluoroethylene), the Stryker-Dacron ligament prosthesis made of Dacron tapes wrapped in a Dacron sleeve and the Gore-Tex ligament augmentation device (LAD) made from polypropylene. These grafts have exhibited good short term results but have encountered clinical difficulties in long term studies. Limitations of these synthetic ligament grafts include stretching of the replacement material, weakened mechanical strength compared to the original structure and fragmentation of the replacement material due to wear.
The ideal ligament or tendon replacement is biodegradable, porous, biocompatible, exhibits sufficient mechanical strength and promotes formation of ligament or tendon tissue.
Various researchers have disclosed potential ligament constructs comprising collagen fibers, biodegradable polymers and composites thereof. For example, collagen scaffolds for ACL reconstruction seeded with fibroblasts from ACL and skin have been described (Dunn et al. The Tissue Engineering Approach to Ligament Reconstruction. Material Research Society Symposium Proceedings 331, 13-18, 1994, Boston, Materials Research Society; Bellincampi et al. J. Orthop. Res. 1998 16:414-420). WO 95/2550 also discloses a prosthetic device for ligament repair comprising an arrangement of collagen threads.
A bioengineered ligament model, which differs from other ligament models in the addition of ACL fibroblasts to the structure, the absence of cross-linking agents and the use of bone plugs to anchor the bioengineered tissue, has also been described (Goulet et al. Tendons and Ligaments. In R. P. Lanza, R. Langer, and W. L. Chick (eds), Principles of Tissue Engineering, pp. 639-645, R. G. Landes Company and Academic Press, Inc. 1997).
U.S. Pat. No. 4,792,336 discloses a device with an absorbable component comprising a glycolic or lactic acid ester linkage. The device comprises a plurality of fibers comprising the absorbable component which can be used as a flat braid in the repair of a ligament or tendon.
The present invention relates to a graft material for use in ligament and tendon repair and reconstruction composed of a degradable, polymeric, fiber-based, three dimensional braided scaffold.